1. Field of the Invention
The present invention relates to a method for producing a semiconductor optical integrated device.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 4-199689 discloses an optical waveguide device in which two optical elements, i.e., a semiconductor laser portion and an optical modulator portion, are monolithically integrated. In this optical waveguide device, each of the semiconductor laser portion and the optical modulator portion has a structure in which a buffer layer composed of InGaAsP, a protective layer composed of InP, a core layer composed of InGaAsP, and a cladding layer composed of InP are stacked, in that order, on one InP substrate. The core layer of the semiconductor laser portion functions as an active layer that generates light. The core layer of the optical modulator portion functions as a light absorbing layer that absorbs light propagating from the semiconductor laser portion. The core layer (light absorbing layer) of the optical modulator portion is directly connected to the core layer (active layer) of the semiconductor laser portion by a butt-joint method. The butt-joint connection between the core layer of the optical modulator portion and the core layer of the semiconductor laser portion is formed by epitaxial growth. Furthermore, in the optical waveguide device, a stripe-shaped mesa structure extending in the direction of light propagation is formed. The stripe-shaped mesa structure includes the core layer of each of the semiconductor laser portion and the optical modulator portion. A buried layer configured to planarize a surface of the device is formed on each side surface of the stripe-shaped mesa structure.